Showing the actual connections between system pairs has another advantage: it lets you represent the architecture as a formal graph, meaning you can compare architectures using standard graph analysis techniques. Even just counting the connections gives a useful measure of relative complexity.

The diagrams above illustrate this nicely: the top picture shows the same architecture as before, which has 14 system-to-system connections (out of 28 possible pairs, another useful metric, even though some wouldn’t make much sense). The bottom picture shows the same systems with everything connecting through a central database: now there are only eight connections and several missing system-to-system links have been provided automatically. If you want a crude approximation of how much a central database reduces complexity (and hence cost), this is good place to start.